Abstract: The upconverter mixer circuit comprises a Gilbert cell with an LC-resonator tuned to the output frequency of the upconverter mixer circuit, and an output buffer. In a preferred embodiment the output buffer comprises a differential amplifier being emitter degenerated with inductances for a low-pass characteristic. The LC-resonator of the Gilbert cell as well as the inductances of the output amplifier are integrated in an integrated circuit together with the other parts of the upconverter mixer circuit and provide a first selection within the integrated circuit for the subsequent stages, for example an intermediate frequency filter of a double conversion TV tuner. When the upconverter mixer circuit is operated with a strong DC-current and hard switching, which is necessary for achieving low noise, strong high frequency parasitic currents are also generated.

Abstract: The reduction of interfering influences in an LC resonant circuit with an integrated circuit is effected by including the interfering elements of the housing in the resonant circuit. This precludes the occurrence of parasitic radio-frequency oscillation modes. It also ensures good radio-frequency properties and a wide frequency tuning range.